1. Field of the Invention
The present invention relates to an anti-skid braking system for an aircraft. In particular, the present invention is directed to an anti-skid or anti-lock braking system for aircraft having a spring loaded, double acting accumulator in series with a master cylinder and a brake cylinder.
2. Prior Art
Large aircraft, such as jet airplanes and turbo prop airplanes, typically have anti-locking braking systems which consist of manipulating the metering spool on a hydraulic boost valve of a power braking system. Smaller aircraft typically do not include power braking systems and do not include anti-skid braking mechanisms. Unlike automobiles and other vehicles, small aircraft typically have independent left side braking systems and independent right side braking systems.
In prior anti-skid braking systems, the wheel speed is monitored to detect a sudden deceleration to initiate the anti-skid braking system.
As various patents in the literature have disclosed, an anti-skid braking system could operate by comparing the wheel speed to the vehicle's speed. This vehicle speed could be derived from a GPS provided signal. No such system is being manufactured for use on a manual aircraft.
For example, Clothier (U.S. Patent Publication No. 2010/0063703) discloses a braking control for aircraft including unmanned vehicles having a first side braking unit for braking a first wheel and a second side braking unit for braking a second wheel. A brake control unit receives independently generated aircraft speed data, such as GPS (global positioning system) data.
Masclet (U.S. Pat. No. 4,367,529) discloses automatically controlling braking of an aircraft wherein function of the true speed of the aircraft is compared with program speed Vp to obtain a different signal.
Hirzel (U.S. Pat. No. 3,724,916) discloses anti-skid braking for aircraft with independently brakable wheels capable of producing signals representative of the changing ground speed and modifying braking action of the individual wheels.
Different types of anti-skid braking systems have also been employed. Krugler, Jr. (U.S. Pat. No. 3,726,568) includes a wheel slip detecting circuit and an hydraulic pressure control piston that pulls fluid from the brake during an anti-skid function. This feature decreases the pressure condition to initiate the anti-skid system.
Some existing anti-lock braking systems require sophisticated digital controllers which require software that is expensive to develop and certify.
There remains a need for a simple and inexpensive anti-skid braking system for aircraft which is operated by an analog electronic circuit.
Accordingly, the present invention is directed to an anti-skid braking system for aircraft providing better directional control and reduced stopping distance on runways and in particular, runways contaminated with debris, water, ice or snow.
The present invention is also directed to an anti-skid braking system for aircraft which reduces flat-spotted and blown tires during aggressive stopping on dry or contaminated runways.
The present invention is also directed to an anti-skid braking system for aircraft providing reduced stopping distance by allowing more aggressive braking on clear and dry runways.
The present invention is also directed to an anti-skid braking system that causes hydraulic fluid to flow to the master cylinder during anti-skid operation, providing direct tactile feedback to the pilot.
The present invention is also directed to an anti-skid braking system having no net fluid volume change in the braking circuit during anti-skid operation due to use of a balanced, double acting accumulator.